Electric oscillator



G. M. J. MACKAY.

ELECTRIC OSCILLATOR.

APPLICATION FILED JAN-27.1916.

1,337,933, Patented Apr. 20, 1920.

2 SHEETS-SHEET I.

Inventor: George TTl. J. mackay,

His )Ittorneg.

G. M. J. MACKAY.

ELECTRIC OSCILLATOR.

APPLICATION F ILED mn.27. 1916.

2 SHEETSSHEET 2.

Fig.2.

Irfiventlor: George TTIJ. mac: ka

Mtorney 1 UNITED STATES PATENT OFFICE.

GEORGE M. J.

MACKAY OE SCHENECTADY, NEW YORK, ASS IGN OR TO GENERAI ELECTRIC COMPANY,A CORPORATION OF NEW YORK.

- ELECTRIC OSCILLATOR.

Specification of Letters Patent.

Patented Apr. 20, 1920.

. Application filed January 27. 1916. Serial No. 74,594.

1 b all whom it may concern:

Be it known that I, Gnome M. J. MACKAY, a subject of the King of GreatBritain, residing at Schenectady, county'of Schenectady, State of NewYork,have invented certain new and useful Improvements in ElectricOscillators, of which the following is a specification.

The present invention comprises an apparatus for producing highfrequency electric oscillations from either direct current or lowfrequency alternating current, and it is the object of my invention toprovide a means for generating oscillations which is of greaterstability than are oscillators heretofore used, and to generate highfrequency waves substantially free from harmonics, and of relativelylarge power. The electrodes being substantially non-consuming and notbeing brought into contact when the arc is started, the arc gap may beaccurately fixed.

The apparatus embodying my invention comprises an oscillating circuitcontaining electrodes, one of which consists of refrac' tory materialoperable at incandescence above about 2000 C. in a gas substantiallyinert with respect to the incandescent electrode and at a pressure highenough to suppress electrical disintegration of the electrodes. Myinvention will be pointed out with greater particularity in the appendedclaims taken in connection with the appended drawings and theaccompanying description.-

Figure 1 shows an arc device with a diagram of electrical connections,and Fig. 2 shows a modification in which the arc of the oscillator issubjected to a magnetic field.

Referring to Fig. 1 of the drawings, the arc is produced in an envelop 1between a cathode 2 and an anode 3 connected respectively by conductors1, 5 to a source of energy 6. The cathode comprises a coiled conductor7, and a more massive pointed arcing tip 8 which is located close to andin good thermal relation to the coil 7 The cathode consists preferablyof ductile tungsten but other refractory materials incandescible at atemperature above about 2000 C. may be used, for example, tantalum. Aheating current may be conveyed to the cathode by the conductors 9, 10which may also consist of tungsten, and which are sealed in the usualway into a stem 11. The anode 3 and its supporting stem 12, preferablyconsist of tungsten but various conductive materials may be used, forexample, carbon, copper, iron or other metals. The anode shouldpreferably have a heatdissipating capacity large enough to enable it tooperate continuously below the temperature at which appreciable electronemission occurs, say about 700 to 800 C. The envelop after having beenevacuated of air and deprived of water vapor is filled with a dry gashaving little or no chemical afiinity for the electrode material when atthe operating temperature. Preferably I employ a gas such as hydrogen inwhich the arc drop, or voltage consumption is relatively high butvarious other gases, for example, nitrogen, carbon monoxid, argon, neon,mercury vapor, or mixtures of the above may be used. lVhen using mercuryvapor the size and heat dissipating capacity of the envelop should beadjusted to keep the envelop at a temperature high enough to maintainthe mercury vapor at the desired pressure.

The pressure of the gas may vary within wide limits but should in allevents be high enough to suppress electrical disintegration of theelectrodes. Ordinarily the gaseous pressure should be materially inexcess of about 50 millimeters of mercury, and preferably high enough tocause most of the energy supplied to-the arc to be expended in the gas.I have used pressures of about two-thirds of an atmosphere with theenvelop at room temperature with good success. Pressures much aboveatmospheric pressure endanger the envelop particularly when the gas issubjected to variable heatmg.

Connected in shunt with the arc is a resonant circuit containing anadjustablecondenser 13 and an adjustable inductance coil 14. There isincluded also in this circuit the primary coil 15 of a transformerloosely coupled with a coil 16, feeding a consumption circuit 17. Theenergy supply circuit 4, 5 also contains a resistance 18.and inductances19, 20.

When starting the device the cathode is first heated from any convenientsource, as for example, a transformer 21. The switch 22 may then beclosed and an arc will pass between the electrodes 2, 3. The heatingcurrent maybe cut off when the cathode is at incandescence and the arcwill continue to pass from the arcing tip 8 to the anode, thus thenecessity of bringing the electrodes into contact is avoided. Nowandering of the are over the cathode occurs with the deof about 8amperes was obtained in the oscillation circuit 23 with a frequency ofabout 32,000. In general the frequency may be obtained approximatelyfrom the relationship 1 21r LC As both the cathode and the anode aresubstantially non-consuming and as the .electrodes are permanentlylocated in the device in a fixed position witlf respect to each other,the length of the arc gap remains constant during the operation of thedevice.

lVhen coupled to an antenna circuit in the usual way frequencies of100,000 and higher have been obtained with a current of 8 amperesespecially suitable for telephonic communication. The distance betweenthe electrodes may be varied with the supply voltage, for example, witha potential of 750 volts the gap may be 6 or 7 millimeters in length.

In some cases greater efficiencies may be obv tained by applying to theare a transverse magnetic field as illustrated in Fig. 2. The

field may be generated by a winding 24 located opposite the arcgap andconnected in series with the generator 6 supplying the arc.

What I claim as new .and desire to secure by Letters Patent of theUnited States, is

1. An apparatus adaptedto generate high frequency oscillationscomprising the combination of a resonant circuit and an electricdischarge device connected thereto, said device consisting of a sealedenvelop containing a gaseous filling at a substantial pressure, asubstantially non-consuming cathode adapted 'to operate atincandescence, and an anode, the gap intervening between said electrodesbeing substantially constant whereby the oscillations produced areregular and largely free from harmonics.

2. An apparatus adapted to generate high frequency oscillationscomprisingthe combination of, a resonant circuit and a discharge deviceconnected thereto comprising a sealed envelop, a tungsten cathode, ananode and a filling of gas inert with respect to tungsten having apressure of at least about millimeters of mercury, the gap interveningbetween said electrodes being substantially constant wherebyoscillations largely free from harmonics may be produced.

3. An apparatus adapted to generate regular high frequency oscillationssubstantially free from harmonics comprising the combination of anoscillating circuit and an electric discharge device connected theretosaid device comprising an anode, a tungsten cathode having a pointedarcing tip and located in fixed arcing relation to said anode, and afilling of gas inert with respect to said electrodes having at operatingtemperatures a pressure high enough to materially suppressdisintegrationof the electrodes.

' In witness whereof, I have hereunto set my hand this 25th day ofJanuary, 1916.

GEORGE M; 'J. MACKAY.

